The present invention relates to a data transmitting system for transmitting data between a central processing unit in an electronic computer system and a terminal apparatus and, more particularly, to a data transmitting method whereby in an electronic computer system for use in banking facilities such as banks or the like, the data regarding the transaction of a deposit and a payment is divided into a plurality of data blocks and transmitted from the central processing unit to the terminal apparatuses.
In an electronic computer system, there are many cases where data concerned with a certain process is divided into a few data blocks and the divided data blocks are transmitted from the central processing unit to terminal apparatuses. In this case, in general, after completion of the output process of individual data block the terminal apparatus requests the central processing unit to transmit the subsequent data block. In JP-B No. 59-39770, there has been shown a method whereby before the process of the individual data block is executed, namely, when the data block is received from the central processing unit, the transmission of the next data block is requested in order to reduce the time which is required to complete the processing of all of the data blocks.
According to this method, while the terminal apparatus is processing the received data block, the next data block can be received. Therefore, there is such an effect that it is possible to reduce the time after the terminal apparatus requested the transmission of the next data block until the next data block is received.
In this case, there occurs such a problem that when the request for transmission of the next data block was sent from the terminal apparatus to the central processing unit, the central processing unit determines that the terminal apparatus has finished the process of the preceding data block, so that an inconvenience is caused. This problem becomes serious in the electronic computer system in the banking facility such as a bank or the like. An example will now be explained with respect to the terminal apparatus at a bank. There is a case where an operator in the bank operates the terminal apparatus to allow the data regarding the identifying process to be output from the central processing unit and to be displayed on the display device of his terminal apparatus. In this case, the data such as amount of balance at the bank, list of accounts of savings of the same name, and the like is transmitted from the central processing unit and outputted on the display device. Therefore, even if a failure occurs in the terminal apparatus while the data is being displayed on the screen, if the terminal apparatus again performs the identifying process to the central processing unit, the same data can be transmitted from the central processing unit, so that no inconvenience occurs. However, an inconvenience occurs when the operator operates the terminal apparatus and allows the data concerned with the depositing process to be outputted from the central processing unit to the printer of the terminal apparatus. Namely, the data to be printed to the customer's bankbook, totalization data, and the like are transmitted from the central processing unit to the terminal apparatus in the form of several data blocks. The central processing unit stores the line number of the bankbook to which the printer of the terminal apparatus has printed the data and the total amount of moneys collected. Therefore, before the terminal apparatus prints the data and totalizes the moneys collected, if the terminal apparatus sends the request for transmission of the next data block to the central processing unit, the central processing unit will interpret that the printing or totalization was normally executed, and update the content stored therein. Therefore, if a failure occurred in the terminal apparatus during the printing or totalizing process, a contradiction occurs between the central processing unit and the terminal apparatus. To prevent such a contradiction, according to the technique disclosed in JP-B-59-39770, control data is added to the data block which is transmitted from the central processing unit to the terminal apparatus, and only when the central processing unit permits a request for transmission of the next data block by use of the control data does the terminal apparatus requests the central processing unit to transmit the next data block before the present data block is processed.
However, according to the foregoing method, no consideration is made to a case where the control data indicative of the timing of the request for transmission of the next data block cannot be added to the present data block which is transmitted from the central processing unit to the terminal apparatus. In this case, there is such a problem that the terminal apparatus cannot request transmission of the next data block before the present data block is processed.
For example, it is assumed that three terminal apparatuses are connected to the central processing unit and only one of these terminal apparatuses can discriminate the control data added to the data block transmitted from the central processing unit. In this case, when the central processing unit transmits the same data block to all of the terminal apparatuses, even if the terminal apparatus which can discriminate the data block to which the control data was added is normally operated, the other two conventional terminal apparatuses among the three terminal apparatuses will erroneously discriminate and process the data block to which the control data was added. In this manner, in the electronic computer system having the conventional terminal apparatuses, even if control data is added to a data block which is transmitted from the central processing unit, the electronic computer system still fails to properly operate due to the untimed submission of a data block.